The present invention relates to a radio wave absorber used in a radio wave anechoic room.
In recent years, use of electric waves has been spread rapidly in the field of mobile communication to realize a higher-grade information oriented society. On the other hand, various electronic appliances have been popularized with the reformative advance of today""s microelectronics technology. With the advance of such information communication technology, however, the influence of unnecessary electromagnetic wave noise, or the like, on apparatuses relevant to precision machinery has become a subject of discussion.
A radio wave anechoic room (radio wave dark room) having no electromagnetic wave reflection is generally used for measurement of electromagnetic wave noise. A radio wave absorber is disposed in an inner wall of such a radio wave anechoic room. Examples of the background-art radio wave absorber used in the radio wave anechoic room include radio wave absorbers made from organic materials such as foamed styrol, foamed styrene, foamed urethane, etc., mixed with carbon black, or the like, to obtain electrical conductivity. Further, the radio wave absorber is used as a stereostructure shaped into a quadrangular pyramid, a triangular prism or a wedge. For example, the radio wave absorber having such a stereostructure is generally produced by: preparatorily foaming not-yet-foamed polystyrol grains into a ball shape having a diameter of the order of millimeters; coating a surface of the ball with powder of an electrically conductive material such as carbon black, or the like; putting the ball in a desired mold; and then heating the mold to thereby secondarily foam the polystyrol grains.
On the other hand, there is proposed a method of producing a desired-shape radio wave absorber, comprising the steps of: locally heating a predetermined folding portion of an assembly member made from a radio wave-absorbent thermoplastic synthetic resin to thereby soften the folding portion; and then folding the assembly member at the folding portion (Japanese Patent No. 2760578).
The quadrangular pyramid-, triangular prism- or wedge-shaped radio wave absorber produced by a method of thermally foaming an organic material such as polystyrol, polystyrene, polyurethane, or the like, however, has a problem that not only the radio wave absorber is bulky but also the radio wave absorber is easy to break by contact, or the like, when it is carried for construction of a radio wave anechoic room.
Further, in the producing method according to Japanese Patent No. 2760578, there is a problem that the work is complicated because the step of locally heating the predetermined folding portion to thereby soften the folding portion needs to be carried out. Further, since the thermoplastic synthetic resin is used, the radio wave anechoic room for carrying out a large electric power test such as an immunity test, or the like, is inferior both in incombustible characteristic and in fire resistance. There is a problem in terms of safety.
The present invention is designed upon the aforementioned actual circumstances. The object of the present invention is to provide a method in which a desired-shape radio wave absorber excellent in working efficiency for construction of a radio wave anechoic room and having incombustible characteristic can be produced easily, and a member which can be used in the method for assembling a radio wave absorber.
In order to achieve the above object, according to the present invention, the member for assembling a radio wave absorber is configured so as to have a incombustible base material capable of assembling a predetermined-shape structure, and radio wave absorbent incombustible materials fixed to predetermined regions of the base material.
Further, the member for assembling a radio wave absorber according to the invention is configured so that the base material has folding groove portions in regions in which the incombustible materials are not fixed.
Further, the member for assembling a radio wave absorber according to the invention is configured so that the base material is constituted by a connected body which is formed by joining a plurality of base material parts to one another by foldable joint members in regions in which the incombustible materials are not fixed.
Further, the member for assembling a radio wave absorber according to the invention is configured so that each of the incombustible materials is constituted by a honey-comb structure which is formed by making incombustible sheets from a slurry containing a water-containing inorganic compound and an electrically conductive material and laminating the incombustible sheets into a honey-comb shape by use of an inorganic adhesive agent.
Further, the member for assembling a radio wave absorber according to the invention is configured so that each of the incombustible materials has a surface constituted by an electrically conductive layer containing an electrically conductive material.
The method of producing a radio wave absorber according to the present invention is configured so as to comprise the steps of: processing a incombustible base material into a shape capable of assembling a desired-shape structure; fixing radio waveabsorbent incombustible materials to predetermined regions of the base material to thereby produce a member for assembling a radio wave absorber; and bonding end portions of the base material to each other while folding the base material in regions in which the incombustible materials are not fixed.
The method of producing a radio wave absorber according to the present invention is configured so as to comprise the steps of: forming a plurality of parts each by fixing a radio wave absorbent incombustible material to a predetermined region of a incombustible base material processed into a desired shape; joining the parts to one another by foldable joint members directly or through a incombustible base material free from incombustible materials to thereby produce a member for assembling a radio wave absorber; and bonding end portions of the base material to each other while folding the joint members.
Further, the method of producing a radio wave absorber according to the invention is configured so that the shape of the radio wave absorber is any one of shapes including a quadrangular pyramid shape, a triangular prism shape, and a wedge shape.
Further, the method of producing a radio wave absorber according to the invention is configured so that folding groove portions are formed in regions of the base material free from the incombustible materials in advance so that the base material is folded in the groove portions.
In the present invention, the member for assembling a radio wave absorber is not bulky and easy to handle because it has a flat shape. Further, when a desired structure is produced by folding the incombustible base material of the radio wave absorber-assembling member or when a desired structure is produced by folding the radio wave absorber-assembling member by the bonding member, a radio wave absorber having the radio wave-absorbent incombustible material fixed to a predetermined region of the structure can be obtained.